Wheeled vehicles and especially in-line, two-wheeled vehicles such as bicycles, motorcycles, scooters, and the like, are popular forms of transportation, exercise, and sport. More recently, such vehicles are being used in particularly rugged environments including operating over unimproved roads and rough terrain, and for stunt riding over stairs and the like. For example, a form of bicycle commonly known as a mountain bike is specifically intended for off-road operation.
Most two-wheeled vehicles are propelled by a chain operably extending between two or more sprockets. One sprocket, commonly known as a chain ring, is driven by a power source such as a crank and pedal assembly. In bicycles, the chain ring is operably secured to a lower hub of the bicycle's frame which is commonly known as the lower bracket sleeve. The crank and pedal assembly usually have an axis of rotation centered along a centerline extending through the lower bracket sleeve.
Chain rings are usually planar disks with teeth along their outer diameter for engaging the chain. In order for the chain ring to operate effectively, it must remain substantially planar and the teeth must remain intact during operation of the vehicle. However, portions of most chain rings remain exposed and extend below the bicycle frame. Accordingly, chain rings are susceptible to bending and damage caused by inadvertent impact with objects.
This susceptibility is increased with off-road and stunt riding of the vehicle. For example, a rider of a mountain bicycle may frequently attempt to jump small objects such as rocks and fallen trees. If the rider executes a jump and in the process lands the bicycle such that a large rock straddles the front and rear wheels, the chain ring can impact the rock causing damage to the chain ring.
Attempts to protect the chain ring from inadvertent impacts have had limited success. For example, U.S. Pat. No. 5,320,583 to van Wingen born Looyen teaches securing a circular disk to the exterior planar surface of a chain ring such that the circular disk and chain ring are substantially parallel to each other and rotatable on the same axis or rotation. As a rider pedals, the chain ring and circular disk rotate about the axis of rotation. The circular disk contacts some objects approaching the chain ring first, thereby protecting the chain ring to a certain degree. However, since the circular disk is directly connected to the chain ring and drive shaft, any bending or damage of the circular disk caused by the impact will likely also bend the attached chain ring or drive shaft. Moreover, such circular disks offer negligible protection from impacts to the chain ring arising from contact with objects positioned toward the inside surface of the chain ring.
Inventors have also attempted to extend a chain ring protector directly from the bicycle's frame. For example, U.S. Pat. No. 5,067,930 to Morales teaches extending a trough-type protector from forward and aft struts mounted to the frame. The curved trough-type protector extends below the chain ring, thereby protecting it from inadvertent impact. A first clamp for securing the forward strut is positioned on a rail of the frame extending forward from the mounting bracket sleeve. A second clamp for securing the aft strut is positioned on rear wheel forks extending rearward from the mounting bracket sleeve. In an effort to allow the through-type protector to accommodate different bicycle designs, a swivel is provided between the first clamp and front strut.
Despite the benefits of the Morales design, it has several drawbacks. For example, a large amount of hardware, such as the first and second clamps, pivot structure, and struts, is required to support the protector, thereby increasing the expense of the structure and time required to mount and align it properly. Similarly, not all bicycles have the frame structure stemming from the mounting bracket sleeve as shown in Morales. Accordingly, the first and second clamps and orientation taught in Morales may not be operable when attempting to install the Morales protector on these different frame structures.
In addition, the length of the struts determines the size of the chain ring that may be used with it. Despite the limited adjustability provided by the swivel, if the struts are too short, a trough-type protector will not extend below the chain ring. Also, if the struts are too long, the trough-type protector can interfere with operation of the bicycle. In addition, under some impacts on the trough-type protector, the swivel structure can actually allow the trough-type protector to deflect into to the chain ring, thereby damaging it, or at least forcing the rider to stop to realign the protector.